The STRO-1+ fraction of adult human bone marrow contains the osteogenic precursors

Abstract

The monoclonal antibody STRO-1 identifies clonogenic bone marrow stromal cell progenitors (fibroblast colony-forming units [CFU-F]) in adult human bone marrow. These STRO-1+ CFU-F have previously been shown to give rise to cells with the phenotype of fibroblasts, adipocytes, and smooth muscle cells. In this study, the osteogenic potential of CFU- F derived from the STRO-1+ fraction of adult human bone marrow was determined. CFU-F were isolated from normal bone marrow aspirates by fluorescence activated cell sorting, based on their expression of the STRO-1 antigen. Osteogenic differentiation was assessed by the induction of alkaline phosphatase expression, by the formation of a mineralized matrix (hydroxyapatite), and by the production of the bone- specific protein osteocalcin. STRO-1+ cells were cultured in the presence of dexamethasone (DEX; 10(-8) mol/L), ascorbic acid 2- phosphate (ASC-2P; 100 mumol/L), and inorganic phosphate (PO4i; 2.9 mmol/L). After 2 weeks of culture, greater than 90% of the cells in each CFU-F colony stained positive for alkaline phosphatase using a monoclonal antibody specific for bone and liver alkaline phosphatase. Alkaline phosphatase activity was confirmed by histochemistry. A mineralized matrix developed in the CFU-F cultures, after 4 weeks of culture in the presence of DEX, ASC-2P, and PO4i. Mineralization was confirmed by both light and electron microscopy. The mineral was identified as hydroxyapatite by electron dispersive x-ray microanalysis and by x-ray diffraction analysis. In replicate cultures, osteocalcin release was shown after exposure of the cells to 1,25-dihydroxyvitamin D3 (10(-7) mol/L) both by radioimmunoassay and Northern blot analysis. This work provides direct evidence that adult human bone marrow-derived CFU-F are capable of differentiating into functional osteoblasts and that osteoprogenitors are present in the STRO-1+ population.

Isolation and Characterization of Human Clonogenic Osteoblast Progenitors Immunoselected from Fetal Bone Marrow Stroma Using STRO-1 Monoclonal Antibody

“…(7) The antigenic epitope that is recognized by STRO-1 has not yet been identified although this is not crucial to its potential as a probe for isolating early precursor cells present in human BM stroma. (7,32) Importantly, STRO-1 does not bind to T and B cells, myeloid cells, megakaryocytes, macrophages, and their progenitors. (7) Although nucleated erythroid cells show some reactivity with STRO-1, most of these are removed by density centrifugation, and survival in vitro of any remaining contaminant is not supported by the culture conditions as used in this study.…”

“…(22,30,31) The second stage was, by analogy with the purification of hematopoietic progenitors from BM, a positive selection procedure based on magnetic activated cell sorting (MACS) and utilizing a murine monoclonal antibody (MAb), STRO-1, (7) which recognizes all the clonogenic stromal precursors in human marrow, including all assayable osteoprogenitors. (7,32,33) With the aim of generating clonogenic STRO-1 + cells, the immunoselected cell population was immortalized with an origindefective mutant of the SV-40 large tumor antigen (T-Ag) (34) and cloned. Using this approach, we isolated a clonogenic immortalized human fetal STRO-1 + stromal cell line with characteristics of osteoprogenitor cells.…”

Dental stem cells and their potential role in apexogenesis and apexification

“…The stromal-derived factor-1 (STRO-1) antigen has become recognized as a putative marker in the isolation and identification of MSC. Anti-STRO-1 identifies a cell surface antigen expressed by MSC which is minimally reactive with haematopoietic progenitors (Gronthos et al 1994). Immunohistochemistry and gene profile analysis have identified perivascular cell markers, CD146/MUC18, 3G5, CD-44, VCAM-1; alkaline phosphatase and a-smooth muscle actin in differing proportions on STRO-1 positive cells from dental tissues (Gronthos et al 2000, Shi and Gronthos 2003, Seo et al 2004).…”

The effects of silicate ions on human osteoblast adhesion, proliferation, and differentiation

“…19,20 STRO-1 is a trypsin-resistant surface antigen present on a subpopulation of bone and marrow cells. The precise function of STRO-1 is unclear, but many studies have associated its expression with multipotential cells including bone marrow cells 21 and renal capillary pericytes. 22 The expression of STRO-1 decreases as marrow stromal cells differentiate into osteoprogenitors and mature osteoblasts.…”